The effectiveness of exogenously administered recombinant human erythropoietin (Epo) has not been closely studied in many infants <1000 grams, the population most at risk for repeated blood transfusions. To determine if their erythroid progenitors are responsive to Epo, light density cells from cord blood of preterm infants <1000 grams will be cultured in various concentrations of Epo. Term cord blood will be used for comparison.